When working material, such as in an extrusion press, a punch member and a die member are utilized such that material to be extruded is placed in a die member and an extrusion punch powered on one end by a force transmitting mechanism is caused to enter the die means, and by compressing the material in the die means, the material flows under pressure into a desired end.
Specifically, in a back extrusion process, the die means is closed on the lower end, and there is sufficient clearance between the inside diameter of the die means and the outside diameter of the punch such that, when the material to be extruded is compressed, it flows axially into the clearance provided between the punch and the die means.
Most punches of the prior art have been formed of a hardened steel material in order to transmit the force required for deformation of the material to be extruded. A steel punch used in a back extrusion process usually has a uniform diameter throughout its length except for the end of the punch which first enters the die means, and this end is provided with a slightly larger diameter such that, when the material that is being extruded flows outward and around the enlarged end of the punch, it will not contact the outer surface of the punch which it surrounds. This is done so that the punch may be extracted from the die means without the extruded material being engaged to the punch.
The material that is extruded is sometimes extruded at an elevated temperature or has heat imparted to it from its mechanical deformation such that, if the extruded material were to stay with the punch as it was retracted from the die means, the immediate cooling of the extracted material would cause it to contract and serious problems would then arise in having to remove the extruded material from the punch before any further extruding would be possible.
One of the problems that arises when using a punch made of a steel material is that, after a certain period of use, the slightly enlarged diameter of the punch is severely galled or worn down due to abrasion of the material as it flows around corners of the punch. When that diameter is worn down, there is no clearance between the extruded material and the diameter of the rest of the punch body and the extrusion punch must then be removed and replaced in order to continue the extrusion operation.
Certain other configurations and methods of construction of extrusion punches and the like have been described in applicants' copending U.S. patent application Ser. No. 644,642, filed Dec. 29, 1975, entitled "EXTRUSION PUNCH AND METHOD OF CONSTRUCTION."
It is an object of the present invention to provide a hard wear resistant material on the tip of the extrusion punch that will significantly outlast any of the steel materials presently used on such extrusion machines.
It is a further object of the present invention to make the hard wear resistant tip easily and quickly replaceable so as to minimize down time required for maintenance on the extrusion machine.
It is a further object of the present invention to join the hard wear resistant material to the already existing steel extrusion punch in such a manner so as to take advantage of the compressive strength of the hard wear resistant material.
It is a further object of the present invention to provide a simple, efficient, easily replaceable mechanical connection between a hard wear resistant material and a rigid body such as a steel body.